import random

list1=[random.randint(0,100) for i in range(20)]
print(list1)

list2=[]
for i in list1:
    if list1.index(i)%2==0:
        list2.append(i)
list2.sort()
list2.reverse()
print(list2)

for i in range(12):
list1[::2]=list2[i]







